A122507 Triangle in which row n contains the first n terms of A018805.

1, 1, 3, 1, 3, 7, 1, 3, 7, 11, 1, 3, 7, 11, 19, 1, 3, 7, 11, 19, 23, 1, 3, 7, 11, 19, 23, 35, 1, 3, 7, 11, 19, 23, 35, 43, 1, 3, 7, 11, 19, 23, 35, 43, 55, 1, 3, 7, 11, 19, 23, 35, 43, 55, 63, 1, 3, 7, 11, 19, 23, 35, 43, 55, 63, 83

Offset

1,3

Comments

Sequence B is called a reluctant sequence of sequence A, if B is triangle array read by rows: row number k coincides with first k elements of the sequence A. Sequence A122507 is the reluctant sequence of A018805. - Boris Putievskiy, Dec 14 2012

Links

Table of n, a(n) for n=1..66.

Boris Putievskiy, Transformations Integer Sequences And Pairing Functions, arXiv:1212.2732 [math.CO], 2012.

Formula

a(n) = A018805(m), where m = n-t(t+1)/2, t = floor((-1+sqrt(8*n-7))/2). - Boris Putievskiy, Dec 14 2012

Example

1
1, 3
1, 3, 7
1, 3, 7, 11
1, 3, 7, 11, 19
1, 3, 7, 11, 19, 23

Mathematica

a1 = Table[ FoldList[ Plus, 1, 2 Array[ EulerPhi, n, 2 ] ], {n, 0, 10}] Flatten[a1]
Module[{nn=20, ep}, ep=Accumulate[2*EulerPhi[Range[nn]]]-1; Table[Take[ep, n], {n, nn}]]// Flatten (* Harvey P. Dale, May 24 2023 *)

Crossrefs

Cf. A018805.

Sequence in context: A205121 A152903 A226522 * A257258 A259325 A094250

Adjacent sequences: A122504 A122505 A122506 * A122508 A122509 A122510

Keyword

nonn,tabl

Author

Roger L. Bagula, Sep 15 2006

Extensions

Edited by N. J. A. Sloane, Jun 16 2007

Status

approved